There have been prior proposals to use magnetised transducer elements for torque measurement the transducer element being a ring attached to a torqued shaft or the shaft itself. In this connection reference is made to U.S. Pat. Nos. 5,351,555, 5,465,627 and 5,520,059 and to published PCT Applications WO99/21150, WO99/21151 and WO99/56099. In these specifications the ring or shaft is of a magnetoelastic material circumferentially magnetised, that is the magnetisation forms a closed loop around the shaft. While such transducer elements are usable in the practice of this invention, other patterns of magnetisation are usable and do not necessarily rely on magnetoelasticity, and other shapes of transducer element may be employed. One other pattern of magnetisation which may be employed in the practice of this invention is longitudinal magnetisation of the transducer region. One form of longitudinal magnetisation is disclosed in International patent application PCT/GB00/03119 filed 14th Aug. 2000 and published under the number WO01/13081.
As already indicated magnetised transducer elements have been previously proposed for torque measurement, particularly for a rotating shaft, in which a magnetic field sensor arrangement is provided adjacent but not in contact with the transducer element to sense a torque-dependent field.
WO99/56099 also discloses the use of such sensor systems to sense forces applied in elongate members (shafts). However, the present applicant is not aware of any previous proposal to apply this technology in the field of accelerometers.